staging: comedi: dt282x: use comedi_timeout()

The wait_for() macro in this driver is a bit nasty. It effects control flow
which according to the CodingStyle is a _very_ bad idea.

The mux_busy() and ad_done() macros are also bad since they rely on a local
variable having a specific name.

Remove these macros and use comedi_timeout() to wait for the analog input
mux busy completion and end-of-conversion. Both of these are detected by
reading the same register and testing different bits. Pass the bits to test
as the 'context' to the callback function.

The dt282x_ai_cmd() function also checks for the mux busy completion. The
'insn' is not available here but passing NULL is safe because nothing
uses it.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>